The Lewis gun (or Lewis automatic machine gun or Lewis automatic rifle) is a World War I-era light machine gun of American design that was perfected and widely used by the British Empire. It was first used in combat in World War I, and continued in service with a number of armed forces through to the end of the Korean War. It is visually distinctive because of its wide tubular cooling shroud around the barrel and its top-mounted drum-pan magazine. It was commonly used as an aircraft machine gun, almost always with the cooling shroud removed, during both world wars.

The Lewis gun was invented by US Army Colonel Isaac Newton Lewis in 1911, based on initial work by Samuel Maclean.[1] Despite its origins, the Lewis gun was not initially adopted by the American military—most likely because of political differences between Lewis and General William Crozier, the Chief of the Ordnance Department.[2] Lewis became frustrated with trying to persuade the US Army to adopt his design and so ("slapped by rejections from ignorant hacks", as he said),[3] retired from the army. He left the United States in 1913 and headed to Belgium, where he established the Armes Automatique Lewis company in Liège to facilitate commercial production of the gun.[4] Lewis had been working closely with British arms manufacturer The Birmingham Small Arms Company Limited (BSA) in an effort to overcome some of the production difficulties of the weapon.[1] The Belgians bought a small number of Lewises in 1913, using the .303 British round, and in 1914, BSA purchased a licence to manufacture the Lewis machine gun in England, which resulted in Col. Lewis receiving significant royalty payments and becoming very wealthy.[3] Lewis and his factory moved to England before 1914, away from possible seizure in the event of a German invasion. The Belgian Army acquired only a handful of his guns, probably only just in double figures. They were not on general issue in the Belgian Army. They were used only in a few forays by motor vehicles, south of Antwerp, against the flank of the invading German Army.

The onset of World War I increased demand for the Lewis gun, and BSA began production (under the designation Model 1914). The design was officially approved for service on 15 October 1915 under the designation "Gun, Lewis, .303-cal."[5] No Lewis guns were produced in Belgium during World War I;[6] all manufacture was carried out by BSA in England and the Savage Arms Company in the US.[7]

The Lewis was produced by BSA and Savage Arms during World War I, and although the two versions were largely similar, there were enough differences to stop them being completely interchangeable, although this was rectified during World War II.[8]

The major difference between the two designs was that the BSA weapons were chambered for .303 British ammunition, and the Savage guns were chambered for .30-06 cartridges, which necessitated some difference in the magazine along with the feed mechanism, bolt, barrel, extractors, and gas operation system.[7] Savage did make Lewis Guns in .303 British calibre; the Model 1916 and Model 1917 were exported to Canada and the United Kingdom and a few were also supplied to the US military, particularly the navy.[7] The Savage Model 1917 was generally produced in .30-06 caliber. A number of these guns were supplied to the UK under lend-lease during World War II.[9]

The Lewis gun was gas operated. A portion of the expanding propellant gas was tapped off from the barrel, driving a piston to the rear against a spring. The piston was fitted with a vertical post at its rear which rode in a helical cam track in the bolt, rotating it at the end of its travel nearest the breech. This allowed the three locking lugs at the rear of the bolt to engage in recesses in the gun's body to lock it into place. The post also carried a fixed firing pin, which protruded through an aperture in the front of the bolt, firing the next round at the foremost part of the piston's travel.[10][11]

The gun was designed with an aluminium barrel-shroud which caused the muzzle blast to draw air over the barrel and cool it. There is some discussion over whether the cooling system was effective—in the Second World War many old aircraft guns which did not have the tubing were issued to anti-aircraft units of the British Home Guard and to British airfields. Other weapons were used on vehicle mounts in the western desert and did not suffer without the tube. They were found to function properly without it, leading to the suggestion that Lewis had insisted on the cooling arrangement largely to show that his design was different from Maclean's earlier prototypes.[12] Only the Royal Navy retained the tube on their deck-mounted AA-configuration Lewis guns.[13]

The Lewis gun used a pan magazine holding 47 or 97 rounds.[14] Pan magazines hold the rounds in a radial fan. Unlike the more common drum magazines, which hold the rounds parallel to the axis and are fed by spring tension, pan magazines are mechanically indexed. The Lewis magazine was driven by a cam on top of the bolt which operated a pawl mechanism via a lever.[11]

An interesting point of the design was that it did not use a traditional helical coiled recoil spring, but used a spiral spring, much like a large clock spring, in a semicircular housing just in front of the trigger. The operating rod had a toothed underside, which engaged with a cog which wound the spring. When the gun fired, the bolt recoiled and the cog was turned, tightening the spring until the resistance of the spring had reached the recoil force of the bolt assembly. At that moment, as the gas pressure in the breech fell, the spring unwound, turning the cog, which, in turn, wound the operating rod forward for the next round. As with a clock spring, the Lewis gun recoil spring had an adjustment device to alter the recoil resistance for variations in temperature and wear. Unusual as it seems, the Lewis design proved reliable and was even copied by the Japanese and used extensively by them during World War II.[15]

The gun's cyclic rate of fire was approximately 500–600 rounds per minute. It weighed 28 lb (12.7 kg), only about half as much as a typical medium machine gun of the era, such as the Vickers machine gun and was chosen in part because, being more portable than a heavy machine gun, it could be carried and used by one soldier.[16] BSA even produced at least one model (the "B.S.A. Light Infantry Pattern Lewis Gun", which lacked the aluminium barrel shroud and had a wooden fore grip) designed as a form of assault weapon.[17]

The first use of the Lewis in the War was by Belgium, in August and September 1914, when the small number available were fitted to a handful of touring and armoured cars and used in a few sorties against German patrols and troop columns. It is stated that as a consequence the Germans nicknamed the Lewis "The Belgian Rattlesnake".,[18] but contemporary German references have not been found. The Lewis was not in service with the regular Belgian Army.

Great Britain officially adopted the Lewis gun in .303 calibre for land and aircraft use in October 1915,[19] with the weapon beginning to be generally issued to the British Army's infantry battalions on the Western Front in early 1916 as a replacement for the heavier and less mobile Vickers machine gun, the Vickers then being withdrawn from the infantry for use by specialist machine-gun companies. The US Navy and Marine Corps followed in early 1917, adopting the M1917 Lewis gun (produced by the Savage Arms Co.), in .30-06 caliber.

The US Army never officially adopted the weapon for infantry use[13] and even went so far as to take Lewis guns away from US Marines arriving in France and replace them with the cheap, shoddy, and extremely unsatisfactory Chauchat LMG[20]—a practice believed to be related to General Crozier's dislike of Lewis and his gun.[21] The US Army eventually adopted the Browning Automatic Rifle in 1917 (although it was September 1918 before any of the new guns reached the front).[22] The US Navy and Marine Corps continued to use the .30-06 caliber Lewis until the early part of World War II.[23]

Australian Soldiers firing at enemy planes during World War I.

The Russian Empire purchased 10,000 Lewis guns in 1917 from the British government, and ordered another 10,000 weapons from Savage Arms in the US. The US government was unwilling to supply the Tsarist Russian government with the guns and there is some doubt as to whether they were actually delivered, although records indicate that 5,982 Savage weapons were delivered to Russia by 31 March 1917. The Lewis guns supplied by Britain were dispatched to Russia in May 1917, but it is not known for certain whether these were the Savage-made weapons being trans-shipped through the UK, or a separate batch of UK-produced units.[24]

British Mark IV tanks used the Lewis, replacing the Vickers and Hotchkiss used in earlier tanks. The Lewis was chosen for its relatively compact magazines, but as soon as an improved magazine belt for the Hotchkiss was developed, the Lewis was replaced by them in later tank models.[25]

The Germans also used captured Lewis guns in both World Wars, and included instruction in its operation and care as part of their machine-gun crew training.[18][26]

Despite costing more than a Vickers gun to manufacture (the cost of a Lewis gun in 1915 was £165,[5] the Vickers cost about £100),[22] Lewis machine guns were in high demand with the British military during World War I. The Lewis also had the advantage of being about 80% faster to build than the Vickers, and was a lot more portable;[27] Accordingly, the British government placed orders for 3,052 guns between August 1914 and June 1915.[5] By the end of World War I over 50,000 Lewis guns had been produced in the US and UK and they were nearly ubiquitous on the Western Front, outnumbering the Vickers by a ratio of about 3:1.[22]

Captain Charles Chandler (with prototype Lewis Gun) and Lt Roy Kirtland in a Wright Model B Flyer after the first successful firing of a machine gun from an aeroplane in June 1912.

The Lewis gun has the distinction of being the first machine gun fired from an aeroplane; on 7 June 1912 Captain Charles Chandler of the US Army fired a prototype Lewis gun from the foot-bar of a Wright Model B Flyer.[18]

The Lewis gun was extensively used on British and French aircraft during World War I, as either an observer's or gunner's weapon or as an additional weapon to the more common Vickers. The Lewis's popularity as an aircraft machine gun was partly due to its low weight, the fact that it was air-cooled and that it used self-contained 97-round drum magazines. Because of this, the Lewis was first mounted on the Vickers F.B.5 "Gunbus", probably the world's first purpose-built combat aircraft, when it entered service in August 1914, replacing the Vickers machine gun used on earlier experimental versions.[28] It was also fitted on two early production examples of the Bristol Scout C aircraft by Lanoe Hawker in the summer of 1915, mounted on the port side and firing forwards and outwards at a 30° angle to avoid the propeller arc.

The need for forward-aimed aircraft mounts for the Lewis gun to avoid firing through the propeller arc on single-engined fighters resulted from the open bolt firing cycle of the Lewis, which prevented it from being synchronized to fire directly forward through the propeller arc of such aircraft; only the British F.B.5, Airco D.H.2 and Royal Aircraft Factory F.E.8pusher fighters could readily use the Lewis as direct forward-firing armament early in World War I. British single-engined fighters could use the Foster mounting to elevate a Lewis gun above the propeller arc for unsynchronized firing, as was used on production S.E.5a fighters and on field-modified examples of the Avro 504. For the use of observers or rear gunners, the Lewis was mounted on a Scarff ring, which allowed the gun to be rotated and elevated whilst supporting the gun's weight.[29] Lewis guns were often employed for balloon-busting, loaded with incendiary ammunition designed to ignite the hydrogen inside the gasbags of German Zeppelins, other airships and Drache barrage balloons.[18]

1918 Sopwith Dolphin with twin Lewis guns aimed upwards.

Later, on the French Nieuport 11 and Nieuport 17 and the British S.E.5a and some versions of the Sopwith Camel and Bristol F2b fighter aircraft, the Lewis was fitted above the top wing on a Foster mount, which allowed firing directly forward outside the propeller arc. The gun could be swung back into the cockpit on a rail to allow the ammunition drum to be changed in flight but fighter ace Albert BallV.C. also discovered that the weapon retained its original trigger and could thus be fired upwards. He used the upward firing Lewis to attack solitary German two-seater aircraft from below and behind, where the observer could not see him or fire back. It was his use of the weapon in this way, in a Nieuport, that led to its later introduction on the S.E.5/S.E.5a. Ball had acted in a consultant capacity on the development of this aeroplane. The later Sopwith Dolphin, already armed with twin synchronized Vickers guns just forward of the pilot and just above its V-8 engine, also could use one or two Lewis guns mounted on the forward crossbar of its cabane structure, between the top wing panels as an anti-Zeppelin measure.

Lewis guns were also carried as defensive guns on British airships. The SS class blimps carried one gun. The larger NS class blimps carried two or three guns in the control car and some were fitted with an additional gun and a gunner's position at the top of the gasbag.[30]

By World War II, the British Army had replaced the Lewis gun with the Bren gun for most infantry use. As an airborne weapon the Lewis was largely supplanted by the Vickers K, a weapon that could achieve over twice the rate of fire of the Lewis.

In the crisis following the Fall of France, where a large part of the British Army's equipment had been lost, stocks of Lewis guns in both .303 and .30-06 were hurriedly pressed into service, primarily for arming Home Guard units and purposes such as defending airfields and anti-aircraft use.[31] 58,983 Lewis guns were taken from stores, repaired, refitted and issued by the British during the course of World War II.[32] In addition to their reserve weapon role in the UK, they also saw front-line use with British, Australian, and New Zealand forces in the early years of the Pacific campaign against the Japanese.[33] The Lewis gun saw continued service as an anti-aircraft weapon during World War II; in this role it was credited by the British for bringing down more low-flying enemy aircraft than any other AA weapon.[34]

A New Zealand-crewed LRDG truck (equipped with a Lewis Gun) is dug out of the sand, c.1942.

American forces used the Lewis gun (in .30-06 caliber) throughout World War II. The US Navy used the weapon on armed merchant cruisers, small auxiliary ships, landing craft and submarines. The US Coast Guard also used the Lewis on their vessels.[34] It was never officially adopted by the US Army for anything other than aircraft use.[13]

The Germans used captured British Lewis guns during World War II under the designation MG 137(e),[36] whilst the Japanese copied the Lewis design and employed it extensively during World War II;[34] it was designated the Type 92 and chambered for a 7.7 mm rimmed cartridge that was interchangeable with the .303 British round.[37][38]

The Lewis was officially withdrawn from British service in 1946,[22] but continued to be used by forces operating against the United Nations in the Korean War. It was also used against French and US forces in the First Indochina War and the subsequent Vietnam War.[26]

Total production of the Lewis gun during World War II by BSA was over 145,000 units,[13] a total of 3,550 guns were produced by the Savage Arms Co. for US service—2,500 in .30-06 and 1,050 in .303 British calibre.[23]

A 12.7×81mm variant developed in 1924 by The Birmingham Small Arms Company Limited also existed.[39][40][41]

There was also a Fremdgerät number for a Leichte MG 107(f), with the original name given as "Fusil-mitrailleur «Lewis» mle 1924", chambered in either 8×50mmR Lebel or in 6.5×55mm Mauser and manufactured by Societe d'Armes Lewis at Saint-Denis; the firing rate given was 450-rounds per minute.[42] One book lists this "Fusil-mitrailleur «Lewis» mle 1924" as a French Lewis gun without further details,[43] but the mechanism appears rather different.[44][unreliable source?]

A short-barreled light machine gun variant also existed during World War II. It came with a hand guard and was fed from 30-round Bren magazines[citation needed].

The German FG42 paratrooper's rifle used the Lewis gun's gas assembly and bolt design which were in turn incorporated into the M60 machine gun.[26] The Russian PKP "Pecheneg" borrows the forced cooling principle.

William McCleave Easterly (1998). The Belgian Rattlesnake: The Lewis Automatic Machine Gun : a Social and Technical Biography of the Gun and Its Inventors. Collector Grade Publications. p. 542. ISBN978-0-88935-236-0.